The coasters communicate by sending messages across the surface. The messages are meant to act as icebreakers between bar patrons, says Tom Bartindale, who invented the coasters with fellow postgraduate student Jack Weeden at Newcastle University’s Culture Lab. “It’s a starting point for an actual conversation,” Bartindale says.

An infrared light source and a camera beneath the partially transparent surface recognize ordinary circular coasters because their white underside causes more light to be reflected (a technique called diffused illumination). A projector, also below the surface, creates a halo around each coaster and shows text messages that spin around them.

When a coaster is first placed on the bar, it is assigned a random gender and sexual preference, says Bartindale. It will then try to “chat up” other coasters within a 60-centimeter range by displaying lines such as: “If I had a chance to rearrange the alphabet, I would put ‘U’ and ‘I’ together,” and, “Are you a parking ticket? Because you’ve got ‘fine’ written all over you.”

“It’s quite a cute idea,” says Eva Hornecker, a lecturer in computer science at Strathclyde University. Others have tried using interactive badges to encourage social interaction, she notes, but those usually require users to enter their own personal details, which can be awkward.

When one beer coaster is contacted by another, it scores the amorous advance depending upon the chat-up lines used, and a preset state of interest. If a potential suitor repeatedly scores badly, the coaster on the receiving end will refuse to talk to it anymore.

One of the problems with other interactive surfaces, Hornecker says, is that they can interfere with using the surface as a table. “This is quite interesting because it turns a supposed limitation into the core of the idea,” she says.

Bartindale says he and Weeden got the idea after a conference in Germany, where lots of people were sat in isolated groups.

The coasters were put to the test last week at the university’s Culture Lab Jam 45, an event that showcases student ideas. “People loved it,” Bartindale says. “And we did notice that people that didn’t know each other were talking to one another, which was encouraging.”